Osteosynthetic bone plates for the treatment of fractures, in particular for the reconstruction of mandibular fractures are fitted intraoperatively in order to fix bone fragments together. This may be necessary in osteosynthesis, following accidents in which a bone has shattered into bone fragments, or in orthognathic/maxillofacial treatment for surgical control of abnormal positioning after an osteotomy, and subsequent positional correction of the bone fragments.
Such a bone plate is used principally to span and fix two bone fragments together, one part of the bone plate in each case being connected releasably to a bone fragment. In order to establish the connection between the temporarily fitted bone plate and the bone fragments, the bone plate has through-holes for the insertion of bone screws which engage in the bone fragments. The bone plates should be able to bend in order to correctly match the bone geometry, but at the same time they must guarantee sufficient stability. These two requirements are in principle mutually contradictory. Moreover, the bone plates should permit the buildup of a pressure between the fragments, which is achieved by the opposite arrangement of what are referred to as compression holes.
DE 23 40 880 A1 discloses a solid linear bone plate which is used for treating jaw fractures and which, spanning the fracture site on the jaw bone, is screwed onto both of the bone fragments that are to be joined together. In each half of the bone plate there are two oblong holes oriented toward the plate center and toward the fracture site. On the side directed away from the jaw bone, the oblong holes have a countersink with a screw seat configured as a beveled plane surface. At least one oblong hole per half is inclined relative to the plate center. On the side directed toward the jaw bone, the bone plate has a projecting notched strut at the center. As a result of the arrangement of the oblong holes and the beveled screw seats, the bone fragments are compressed toward the fracture site when the inserted bone screws are tightened; the pressure thus built up between the fragments results in improved healing of the bone fracture.
However, because of it's rigidity, this plate cannot readily be adapted to the existing bone geometry. A rigid plate which cannot be sufficiently bent to fit the jaw bone has the effect that the bone fragment less anchored in the jaw is moved toward the plate, and dislocations therefore occur. Even slight shifts in the fracture area lead to the loss of the interfragment support, which results in greater mobility within the fracture area. The simple hole pattern on the plate additionally permits little variability in terms of attachment to the bone fragments. For example, in Prein, J. (editor): Manual of Internal Fixation in the Cranio-Facial Skeleton, Springer-Verlag Berlin 1998, page 30, straight or arcuate bone plates with compression holes for treating fractured mandibles are shown which have a thickness of 1.65 mm or 2.0 mm, respectively, and are designed for bone screws with an external thread diameter of 2.4 mm.
Thinner bone plates, for example with a thickness of between 0.5 mm and 0.9 mm, which can be bent more readily, are known in craniofacial applications (cf. Prein, loc. cit., page 28). Different configurations have been developed for this purpose, for example the L-plate, Y-plate, T-plate, H-plate, X-plate, double Y-plate or frame plate. Bone screws with an external thread diameter of 1.0 mm to 2.0 mm are used for these. However, these bone plates have no compression holes, but only simple cylindrical screw holes with countersinks for partially receiving the screw head. The provision of compression holes in these thinner plates has been avoided because opinion hitherto held that a greater plate thickness, for example 1.65 mm or 2.0 mm, was necessary for building up a pressure between the fragments. In addition, with the previously available production technology, it would have been extremely complicated to work compression holes into thinner bone plates, for example with the thickness of 1.0 mm.
According to the prior art hitherto disclosed, no bone plate has as yet been made available in which, even when absolutely correctly applied, sufficient stability for unimpeded bone healing is guaranteed and a pressure can be built up between the fragments for the dynamic compression for improved bone fracture healing. Particular requirements exist for example in respect of:                fractures of atrophic jaws;        unstable oblique fractures;        infected mandibular fractures;        unstable jaw angle fractures; and        mandibular fractures in noncooperative patients.        
In view of the cited shortcomings of the bone plates known to date, the object of the invention is to make available a bone plate particularly for the treatment of mandibular fractures, which, as a result of greater deformability, can be readily bent to the respective contour of the bone fragments, but which nevertheless guarantees a secure and positionally stable fixation of the bone fragments. That is to say, the bone plate must be easily deformable on the one hand and yet must have adequate rigidity on the other. Moreover, the bone plate is to have compression holes in order to be able to generate a pressure between the fragments—in the sense of compression osteosynthesis—for promoting the bone healing. Furthermore, the bone plate to be produced must not pinch the nerve issuing at the mandible and, in the event of comminuted fractures, small bone fragments must also be able to be fixed individually on the bone plate. Finally, the bone plate must be able to be applied using conventional bone screws and must be able to be produced economically in series.